A032660 a(n) is the smallest positive k such that k concatenated with k + n is a lucky number.

3, 6, 1, 2, 1, 4, 5, 6, 59, 2, 1, 4, 5, 6, 1, 6, 3, 2, 3, 10, 7, 2, 7, 4, 3, 4, 1, 14, 1, 2, 5, 10, 1, 2, 1, 2, 3, 6, 7, 2, 1, 14, 21, 10, 11, 6, 3, 4, 5, 6, 1, 12, 9, 34, 3, 22, 11, 2, 1, 2, 15, 18, 1, 12, 3, 2, 9, 6, 1, 12, 1, 2, 5, 4, 5, 8, 13, 8, 5, 4, 7, 2, 3, 2, 9, 4, 5, 2, 1, 8, 3, 4, 1, 6, 1

Offset: 0

Author

Patrick De Geest, May 15 1998

Keywords

• nonn
• base

Comments

First terms of sequences A032640-A032649, continued with displacements n > 9.

Examples

			77th term = 13: 13 + 76 (=77-1) = 89: '13' and '89' = 1389 equals a lucky number.
		

Links

• Michael De Vlieger, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A000959, A032661.

Programs

Mathematica

Block[{L = Array[2 # + 1 &, 10^5 + 1, 0], m, n, r, s}, For[n = 2, n < Length[L], r = L[[n++]]; L = ReplacePart[L, Table[r*i -> Nothing, {i, 1, Length[L]/r}]]]; m = Max[L]; Array[Block[{k = 1}, While[And[# < m, FreeQ[L, #]] &@ Set[s, FromDigits@ Join[IntegerDigits[k], IntegerDigits[k + #]]], k++]; If[s <= m, k, -1]] &, 95, 0]] (* Michael De Vlieger, Jun 24 2020, after Jean-François Alcover at A000959 *)